1. Field of the Invention
The present invention relates to the tensile testing machine of variously cross-sectioned materials, and in particular for tensile testing of such variously cross-sectioned materials as sheets, wires, rods and pipes.
2. Description of the Related Art
The present inventor developed a new method and machine for tensile test of sheet materials as described in Japanese Patent Publication No. 3-47448 (1991-47448) and Japanese Patent Publication No. 4-31053 (1992-31053).
According to this method, a test specimen is gripped by each pair of rolls respectively at each end of a specimen, these rolls are rotated at the standing positions in the direction reverse to each other to stretch out the specimen so that the point of non-displacement appears at the center of specimen with the same rotating speed of all the rolls. The constant strain rate test is performed easily by using parallel-shaped straight specimens where it is possible to realize the continuous microscopic observation of such mechanical properties of sheet materials as deformation of crystal grains and slip pattern during plastic deformation.
In the tensile test of the above-described machine, however, there was an unfavorable problem in the measurement of tensile load caused by a fairly big friction between the rail and the movable roll stand on the rail.
It is necessary to solve new various technical problems for more accurate measurement of tensile force.
Further it is also necessary to develop a quite new system very different from the automated one in the traditional tensile testing machines, for full automation of tensile test.
From the above described point of views, the present invention aims at the development of a tensile testing machine of variously cross-sectioned materials which is of concise construction and make possible more accurate measurement of tensile properties.
Another object of the present invention is to provide a fully automated tensile testing machine of variously cross-sectioned materials.
For achievement of the above-described objects, the tensile testing machine of variously cross-sectioned materials according to the present invention is characterized by hanging at least one of the roll stands in which a test specimen is gripped and elongated by the rotation of gripping rolls and is also characterized by successfully removing the outer effect on the measurement of tensile force.
The present unique automated system is benefited by the features of the present testing method, to make possible a very high efficient rate of feed-in and feed-out system and simultaneous measurement of various tensile properties.
The tensile testing machine equipped with various functions as described above according to the present invention is available for assuring high efficiency, low energy consumption and high reliability in simultaneous measurement of tensile force, work hardening index n, normal anisotropy ratio r and the other tensile properties in fully automated continuous and long time tensile test of sheet materials.
The invention is characterized by freely hanging one or both of the roll stands which have the gripping rolls for a variously cross-sectioned test specimen and, if necessary, is equipped with a device to give a certain initial load to load cells placed between the two roll stands before the start of tensile test.
In the invention, a cleaning device for keeping the optimal surface of gripping rolls by brushing during the operation of tensile test can be provided.
It is impossible to brush the gripping surface during tensile test in the traditional tensile testing machine, while the present invention makes it possible to clean the surface of gripping rolls with brushes simultaneously during tensile test.
The invention provides an extensometer, which has two probes lightly touching respectively to the end points of gauge length for measurement of elongation in tensile.
The invention provides another extensometer, which has two small rolls touching respectively to the end points of gauge length, keeping the initial distance between the rolls and measuring the elongation of a specimen with the rotation of the two rolls.
The invention also provides gripping rolls which have uneven surface profiles striped in the axial direction of rolls or in symmetrical inclination to the axial direction. Two or more uneven surface profiles in the circumferential direction and a constant diameter with the gripping range or small crown in the invention are provided.
The invention further provides a measuring device of specimen width or thickness touching two small rolls to the specimen and detecting the position of a supporting point in the center of two rolls as the average value between the touched points of two rolls.
The invention additionally provides cartridges for containing specimens, feed-in device of specimen from the cartridge, measuring devices of specimen width and thickness before the start of test and an extensometer for measuring the elongation of specimen.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.